The present invention relates generally to power driving apparatus and, more particularly, to apparatus for resonantly driving tools of various types to work on earth, coal, wood, concrete, asphalt or other materials or substances.
Various forms of power sources, mechanical, hydraulic, pneumatic or others, are used to drive tools for different purposes, for example, digging coal, cutting trees, driving piles, pavement removal, earth working, and various agricultural operations. The specific tool is designed for the particular job.
Recently, a power source has been developed employing a resonant vibration system driven by an oscillator, an example being shown and described in U.S. Pat. No. 3,367,716. While the resonant vibration principle has merit in that considerable force can be generated, the proper transfer of such force to the material has proved extremely difficult to accomplish.
The principal advantage of a resonant drive system, as described herein, is that the vibrating element can be supported at its nodes, which are basically stationary. As a result, the transfer of the input forces to the resonant system to the frame is minimized.
It has been found that the location of the nodes in a resonant system varies widely with relatively small changes in operating frequency. In use, when the resonant system encounters a load, the frequency of the system will tend to decrease. Any such decrease in frequency moves the location of the effective nodes, and the supporting frame is no longer attached to the resonant system at the nodes. The net result is that the input vibrational forces are transmitted directly to the frame, with potentially catastrophic consequences.